Electronic buzzer

Abstract

A miniature electronic buzzer for an electronic watch has two vibrating plates with a sealed space between them forming an air spring. One of the vibrating plates carries an amarature which is acted upon by an electromagnetic to vibrate said plate. Vibration is imparted to the other vibrating plate by the air spring. The two vibrating plates and coupling air spring constitute a vibrating system having two resonant frequencies in the audible range. The electromagnet is energized by current having a frequency in the neighborhood of these resonant frequencies. There may be a third vibrating plate coupled with the second vibrating plate by a second air spring. In this event the vibrating system has three resonant frequencies in the audible range.

What is claimed is: 
     
       1. A miniature electronic buzzer comprising in combination a driving means, a vibrating assembly composed of a first vibrating plate and a secondary vibrating plate and a sealed air space between said two vibrating plates, wherein said driving means drives said first vibrating plate by a mechanical power generated from an electronic input signal, and vibration of said first vibrating plate is transmitted to said secondary vibrating plate through said sealed air space, and vibration of said secondary vibrating plate generates a sound wave to the air, both of two resonant frequencies generated from said secondary vibrating plate being audible, and said driving means having a frequency in the neighborhood of said two resonant frequencies. 
     
     
       2. An miniature electronic buzzer according to claim 1, wherein said vibrating assembly comprises a third vibrating plate and a secondary sealed air space between said secondary vibrating plate and said third vibrating plate, said third vibrating plate being driven by vibration of a secondary vibrating plate through said secondary air space, and vibration of said third vibrating plate generating a sound wave to the open air, said driving means having a frequency in the neighborhood of three resonant audible frequencies generated by said third vibrating plate. 
     
     
       3. A miniature electronic buzzer for an electronic watch comprising a base plate of magnetic material, a center pole of magnetic material projecting up from the base plate, a winding around said center pole, a magnetic ring member projecting up from said base plate and surrounding said coil, a first vibrating plate disposed above said center pole and magnetic ring member with an air gap between them, means supporting said first vibrating plate by its periphery, a second vibrating plate disposed above and spaced from said first vibrating plate, means supporting said second vibrating plate by its periphery and sealing the space between said vibrating plates to form an air spring coupling said vibrating plates with one another to constitute a vibrating system having two resonant frequencies in the audible range, an armature of magnetic material on the first only of said vibrating plate so as to provide a magnetic loop comprising said armature, said magnetic ring member, said base plate and said center pole, and energizing means for supplying driving current to said coil with a frequency in the neighborhood of said two resonant frequencies to produce vibration of said first vibrating plate magnetically, the vibration of said first vibrating plate being transmitted to said second vibrating plate by said air spring. 
     
     
       4. A miniature electronic buzzer according to claim 3, in which said energizing means supplies driving current to said coil with a frequency between said two resonant frequencies. 
     
     
       5. A miniature electronic buzzer according to claim 3, in which said energizing means applies to said coil a driving current having components with frequencies corresponding respectively to said two resonant frequencies. 
     
     
       6. A miniature electronic buzzer according to claim 3, in which said energizing means supplies to said coil a driving current which is intermittently changed between said two resonant frequencies. 
     
     
       7. A miniature electronic buzzer according to claim 3, in which said first and second vibrating plates are of the said diameter. 
     
     
       8. A miniature electronic buzzer according to claim 3, further comprising a third vibrating plate disposed above and spaced from said second vibrating plate and means supporting said third vibrating plate by its periphery and sealing the space between said second and third vibrating plates to form a second air spring coupling said second and third vibrating plates with one another to provide with said first vibrating plate and said first mentioned air spring a vibrating system having three resonant frequencies in the audible range, said energizing means supplying to said coil driving current having a frequency in the neighborhood of said three resonant frequencies. 
     
     
       9. A miniature electronic buzzer according to claim 8, in which said first, second and third vibrating plates are of the same diameter.